Message transmission



May 12,1931. A. B. CLARK 9 MESSAGE TRANSMISSION Filed Feb. 2, 1929 5 Sheets-Shae; 1

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mvENToR WITNESSES Q 45 1 7 I ATTORNEY May 12, 1931., A. B. CLARK MESSAGE wamsrussrori Filed Feb. 2, 1929 5 Sheets-Sheet z I I l I I I I I I I I I I INVENTOR.

ATTORNEYS May 12, 1931, A. B. CLARK MESSAGE TRANSMISSION Filed Feb. 2. 1929 5 Sheets-Sheet a INVENTOR ATTORNEYS May 12, 1931. A. B. CLARK 53 LE'SSAGE TRANSMISSION Filed Feb. 2 1929 5 Sheets-Sheet 4 4 7 I IZ VIIIIIIII/IIIIIIIIIIIIIIIIIIIII IIII1 7 1114 I 7IIIIIIIIIIIIIIIIIIIIII/IIIIIIII/l III/I"IIIIIIII/II/(II//)IIIIIII4 IIIlIIlII/IIIII- INVENTOR WITNESSES 4 7 I ATTORNEYS May 12, 1931. L RK 1,805,390.

. MESSAGE IRANSHISS ION Filed Feb. 2, 1929 5 Sheets-Sheet 5 I INVENTOR W\ITNESSES' r I v JZZ I'fZ. 61m% 224% Q/Qy BY v v ATTORNEYS Patented Ma 12, 1931 PATEN Farce ALBERT B. CLARK, OF DOB-CHESTER, MASSACHUSETTS, ASSIG-NOR 0F IOR'IY PER GENT TO ALFRED H. HOWARD, 0F BOSTON, MASSACHUSETTS MESSAGE TRANSMISSION Application filed February 2, 1929. Serial No. 336,994.

This invention relates to message transmission. I

It is among the objects of the present invention to provide a system of and an appa- 5 ratus for the transmission of a plurality of messages simultaneously over a single carrier wave or electrical conductor.

In connection with the present invention, it will be understood that the term message is used in its broadest sense andthat the invention' is not confined tothe specific transmission ,of code messages or other transmission of intelligence in the form of words, but may be used as will be hereafter seen in the transmission of impulses from a piano or other musical instrument.-

Another object of the present invention is to provide a message transmission system and apparatus therefor, which utilize in part television ap aratus.

Another 0 ject of the present invention is to provide means for effecting an automatic synchronism attachment for scanning discs.

efi'ecting of improved means for the operation of an automatic typewriting or printing machine, used in conjunction with the present invention or in accordance with the principles thereof.

Numerous other objects and-features of the present invention include the improved method and the novel apparatus for carrying out the method.

It will be seen that the apparatus'is simple in-construction and efiicient in operation and is adapted to the demands of economic manufacture. i

The foregoing andother objects of the to. Fig. 3is a sectional view illustrating'the some of the principles of the present day Still another object of the invention is the typewriter or printing machme.

present invention will be apparent from the signal lam s, the scanning disc, and the photoelectnc cell assembly;

Fig. 4 is a front elevation showin the scanning disc and the associated signal lamp housing;

Fig. 5 is a view similar to Fig. 3 of the receiving disc and associated apparatus;

Fig. 6 is a detail illustration of one form of synchronizing apparatus formed in accordance with the present invention;

Fig. 7 is a detail sectional View illustrating the construction of a piano key for use in connection with the present invention;

Fig. 8 is a transverse section illustrating one method of operating a pneumatic piano in accordance with the present invention;

Fig. 9' is a diagrammatic illustration of a modified method of controlling the scanning disc and the. associated signal lamps;

Fig. 10 is a detail illustration of a signal recordingmeans formed in accordance with the present invention;

Fig. 11 is a diagrammatic illustration of that portion of my invention which is designed for the operation of an automatic Referring more particularly matically illustrated as including a lurality of circuit controlling devices 10, which, for the sake of conventionality, are shown as simple telegraph keys adapted for the transmission of dot-and-dash telegraph code messages. The circuit for each key'includes the common source of potential, indicated at 11, each key being arranged to control the energization of one of the electric bulbs 12. Each respective key 10 and is arran ed in such manner as to separately control t e illumina tion of the lights 12 by the associated keys 10. In connection with this portion of the appa ratus, it will be understood that the method and apparatus herein disclosed is not confined to this specific manner of controlling'the energization of the light source and that, as will be hereinafter described in connection with Fig. 7 other equivalent means for controlling to Fig. of the drawings, the invention is herein diagramof the lights 12 is associated through a. con ductor 13 with the source of potential 11, the 1 circuit to which light is completed through it's thus other circuits and circuit-controlling means may readily be utilized in connection with the invention.

From the foregoing it will be seen that each of the lights 12 is individually caused to become illuminated in response to the associated key. The lights 12 are arranged to form a bank of lights with which is associated means for intermittently allowing each light of the bank to effect an electrical circuit, the arra-ngement being substantiallysimilar to certain principles now successfully utilized in connection with television transmission. A specific and preferred embodiment of the bank of lights and the intermittent means referred to, is illustrated in Figs. 3 and 4, and will be hereinafter described in detail.

For efiectin g the intermittent projection of light from the lamps 12 to effect a circuit, a scanning disc 15 is provided, preferably provided with a plurality of apertures 16, one of such apertures being provided for each of the lamps 12 and arranged in spiral formation through the disc 15 in such manner that the aperture 16 corresponding withanyone lamp 12, is designed to pass before the lamp and to permit the projection of light therethrough once for every complete revolution of the disc 15. The arrangementis such that during the projection of light from any one of the lamps 12 through its corresponding aperture 16 in the disc 15, the projection of light from any of the other lamps is prevented. The disc 15 is adapted for rotation by a suitable motor 17 associated with a source of potential 18 and -rheostat 19 for controlling the speed of the volved at a speed considerably greater than the speed of electrical impulses illuminating the lamps 12, for each period of illumination of any lamp 12, the corres onding aperture of the disc 15 .Will move be ore the lamp one or more 13111168130 effect impulses in the circuit 21 in response to such illumination, the result being that a plurality of images, one from each of the lamps 12, are broken or chopped and successively control the circuit 21 at a hi h rate of succession.

t will be understood in connection with the present invention that the circuit 21 may be part of a wired circuit of telephone or telegraph arrangement, or, if desired, may be of the Hertzian wave transmission type, as herein illustrated.

Referring more particularly to Fig. 2, the receiving arrangement designed for use in connection with the transmission system above described, includes a receiving circuit which is used in connection with the Hertzian wave form of transmission and a receiv ing antenna 25, detector 26, and amplifier 27, which are adapted to receive, detect and amplify the Hertzian carrying wave upon which are superimposed the electrical impulses, through the medium of the photoelectric cells and the associated apparatus. The output of the amplifier includes the circuit 28, by means of which a source of illumination, such as a neon tube 29, is energized and illuminated in response to the rapid successive illumination ofthe lamps 12. it will be understood that in the use of the present invention with wire telegraphy, the circuit 28 is directly associated with the circuit 21, the amplifier, transmitter, detector and the antenna being displaced by suitable wired transmission ad juncts, such as relays or the like.

For segregating the impulses energizing the tube 29 into their component impulses, a receiving scanning disc 30 is provided, in which apertures 31 preferably provided with lenses therein, are arranged in identical conformity with the apertures 16 of the scanning disc 15, the scanning disc 30 being arranged for rotation by an electrical motor 32 energized through a source of potential 33 and controlled by a rheostat. 1t will be under- 100 stood that in accordance with the principles of television, the discs 30 and 15 are caused to rotate in an accurately synchronized manner.

In view of the fact that this synchronism of the discs is highly important to the success- 105 ful operation of the system, and, as a matter of fact, to the successful operation of any system using the television rinciples, means have been herein disclosed or providing for automatic synchronism thereof, the means be- 110 ing more specifically illustrated in Fig. 6 of the drawings, and will be hereinafter described in connection with that figure.

' Arranged before the scanning disc 30, a battery'of photoelectric cells 35 is provided 5 similar to the battery of lamps 12. One specific arrangement of the relation of the tube 29, disc 30 and cells 35 has been described inconnection with Fig. 5 and will be herein discussed in connection therewith. It

will be understood, however, that the cells 35 are arranged in substantially the same man-v ner as the lamps 12, the arrangement being such that the illumination of the neon tube 29 is periodically adapted to successively afi'ect the cells 35 in such manner that impulses in response to the periodic projection of light thereon throughthelenses 31, will, through the medium of circuits 36, and, if desired, amplifying means 37, operate a relay 38 or be readi y seen from the foregoing that each of the relays 38 is controlled by one specific lamp 12 and that the device 38 will be intermittentl operated in accordance with the illumination of the lamp, and that as the interruptions through the medium of the disc 15 are of high speed, a substantially constant message may be imparted from the keys 10 to the relays 38.

From the foregoing it will be seen that the present invention operates primarily on the principles of television, the picture to be transmitted being displaced by the bank of lamps 12, separate intermittent projections of light from which are received by the photoelectric cell which combines the successive intermittent projections of light into a sin le signal wave which is directed in a suita le manner to the neon tube 29, which by association with the disc and hotoelectric cells 35, divides the signals back nto their original components, permitting each signal to affect an associated relay, as will be clearly understood to those skilled in the art to which this invention relates.

Referring more particularly to Figs. 3 and 4 of the drawings, as hereinbefore described, there is herein illustrated a specific form'of my invention, in which the lamps 12 are enlarged and elon ated to provide a tier of horizontally associated elongated lights 12 positioned within a suitable camera casing 40 including a focusing lens 41, and, if desired, a ground glass or other similar screen 42,-upon which the various illuminations of the lamps 12 are projected, and before which the scanning disc 15 is adapted to revolve. Adjacent the scannin disc and arranged to direct light projecte through any one of the apertures 16 of the disc, a second lens 43 is provided, which concentrates the light'admitted through the aperture 16 upon the photo electric cell 20. Referring more particularly toFig. 4, one preferred embodiment of the apertures-16 showing their spiral posi-- tion, is here disclosed. It will be understood from the foregoing, as disclosed in connection with Fig. 1, the intermittent illuminations of. the lamps 12 are designed to be combined through the medium of the scanning disc 15, to intermittently energize the photoelectric cell 20. 7

Referring more particularly to Fr 5 of the drawings, as hereinbefore described, there is presented a specific structure of the receiving arrangement which includes the tube 29 arranged for illumination in response to the.

composite signal given by means of the photoelectric cell 20, before which the apertured screen disc-3O is adapted to rotate. On the opposite side of the disc 30, a set of concentrating lenses 45 is provided, which directs the illumination pro ected through the aperture 31 of the disc 30 upon the bank of the photophotoelectric cell 35. Thephotoelectric cells 35 are designed for association with the relays 38, as disclosed in connection with Fig. 2 of the present drawings.

For providing accurate synchronism between the movements of the scanning discs 15 and-30, there is provided an improved and novel synchronizing system which will be more clearly illustrated in connection with Fig. 6 ofthe present drawings, but which has been illustrated as applied in connection with Figs. 1, 2, 5 and 9 of the drawings. In the present system there is provided in the bank of lamps 12, a separate constantly illuminated synchronizing lamp 50, together with a synchronizingaperture (not shown) in the disc 15, which is adapted to intermittently permit the projection of light from the lamp 50 to the photoelectric cell20, the positioning of the synchronizing aperture of the disc 15 being arranged in spaced relation to the associated apertures of the disc, whereby the light transmitted therethrough will not interfere. with the signal light being transmita synchronizing aperture similar to the aper-- ture described in connection with the disc 15, the arrangement being obviously such that the periodic synchronizing signals sent out over the circuit 21 are received by and similarlyenergize the tube 20 and when the disc lOQ 30 is properly synchronized with movements of the disc 15, the synchronizing illumination of the tube 29 will pass directly through the synchronizing aperture of the disc 30.

By specifically referring to Fig. 6 of the drawings, there is provided in conjunction with the scanning disc 30, a pair of spaced photoelectric cells'5l arranged in a circle describedby the revolution of the synchronizing a erture of the disc 30. Associated with eac of the photoelectric cells 51, amplifiers 52 are provided and their tubes associated with a suitable relay illustrated as includingelectromagnets 53, and armatures 54, the arran ement being such that when light strikes t e photoelectric, cell 51 at the right in the drawings, a circuit includinga solenoid 55 and conductor 56 is completed and thus the'solenoid 55 is energized. Should light strikethe photoelectric cell 51 on the left of the drawing, a similar solenoid ,57

of the photoe rectilinearlyplaced with respect to the sole noid 55, is ener 'zed through the conductor 58, the return circuit for both solenoids including a conductor 59 with which a suitable source of potential 60 is associated.

In conjunction with the solenoids 55 and 56 and operablein response to energiz'ation thereof, a valve 61 controlling the movement of a suitably actuated plunger 62, is provided, the arrangement being such that when light strikes the photoelectric cell 51 asso ciated with the solenoid 57, movement of the valve 61 is to the right, thus uncovering a port 63 and driving the plunger 62 to the right. The port 64is uncovered by the reverse movement of the valve 61, which may be had through energization of the solenoid 55. Associated with the plunger 62. and operable thereby, a piston 65 is provided. For

controlling the resistance of the motor 32, for driving the scanning disc 30, the means herein disclosed includes a chamber 66, containing a resistance conducting fluid 67, together with a fixed electrode 68 associated with one side of the motor 32, while the piston 65 is associated with a cooperating electrode 69 associated with the opposite-sides of the motor, the arrangement being such that the distance between the electrodes 68 and 69, controls the resistance of the circuit, and as the position of these is controlled through the energization of the hotoelectriccells 51, it will be understood t at the motor speeds are directly responsive to such energization.

Referring again to the synchronizing ap erture of the receiving disc 30, which is disclosed as at 70, as herein described one of the discs 15 and 30 is in proper alinement and properly s chronized,the synchronizing impulses of t e tube 29 is given at a time when w the synchronizing aperture 70 is. directly between the photoelectric cells 51 and that by the time the aperture 70 has reached one or the other of the cells 51, the signal im ulse has been completed and thus neither of t e photoelectric cells 51 is ener ized. On the other hand, should the speed of the disc 30 increase or diminish over that of the speed of the disc 15, the aperture 70 will receive the signal im ulse when it is in line with one or the" ot er of the photoelectric cells 51, the photoelectric cell to the left in Fig. 6 beingenergized when the speed of rotation of t e disc 30 is increased, and conversely the opposite photoelectric cell being energized when the s d of the disc 30 is' below that of the speef i the disc 15. When the a rture 70 registers at the time of the s c ronizing impulse with one or the otliia r ectriccells, the cell is energized and its associated solenoid ener ed in a manner to cause movement 0 the plunger 62 and thus vary the resistance in the motor 32 in a manner to rectify the speed ings, are here shown as supplanted by a piano key controlling member mcludin akey 75, adapted to actuate a plunger 76 w ich moves in a resistance fluid conductor 77, the downward movement of the key increasing the reception of the plunger 76 within the fluid 77, thereby decreasing the resistance in the key circuit, one side of which is associated with the plunger 76 while the other side is associated with the fluid 77. Thus the energization of the lights 12 is both in accordance with and in the key 75. ra By referring to Fig. 8 the relays 38 of Fig. 2 have been displaced by an electromagnet" 7 8 adapted to operatea valve'79 in the tracker bar of the piano, in a manner to control playing-of associated keys.

In connection with Figs. 7 and 8 of the drawings, it will be seenthat the arrangement is such that a piano or similar instrument may be effectively operated throu h the medium of the present invention, an that through the use of the device as illustrated, not only are the specific impulses transmitted to the receiving piano, but in addition the technique of the player is reproduced.

Referring more particularly to Fig. 9 of the drawings in conjunction with Fig. 1, in which the complete transmitting arrangement has been illustrated, there is here provided an improved means by which the intermittent successive projection is stepped up. In this instance t e disc 15 is provi ed proportion to the movement of with a plurality of apertures for each of the lamps 12, and a circuit controller including troller and four groups of the lam s 12, to-

gether with four apertures for eac one of the lamps in the scanning disc 15. The arrangement is such that as the quadrant of the thro h the circuitcontroller 21, asses before tiese to permit energization of scanning disk 15, which for instance" to move through the medium of a suitable the group. A of lamps 12,energization thereofpermitted and suchenergization 1s some by those'apertu'res in this sector which correspond with these lamps. ,As the disc moves into the thenext adjacent group of lamps is permitt'ed to be ener 'z'ed duringpassage of this -quadrant therebepresent invention,

1 connection the lamps in a single apparatus may be utilized. Thus a greater number of messages may be sent. It will be understood in this that the receiving arrangement is' similarly constructed by the provision of a circuit controller, whereby the segregation of the messages is properl vefiecte Referring more particu the'drawings, there is here disclosed an apparatus 'forrecording the messages received tive material, the arrangement being such.

and segregatedby the receiving disc 30, the arrangement including the neon tube or other light source/29, which is controlled by the photoelectric cell 20 and before which passes the scanning disc 30 with its apertures 31. The opposite side of the scanning disc 30 is adjacent" a concentrating lens 85, which directs the segregated light impulses through a slit 86 in a partition 87 within a cabinet 88 housing the apparatus. 'Before the slit 86, a plurallty of suitable tapes 89 are caused motor 90 and associated drum. The tapes 89 are preferably formed of some lightsensithat the intermittent flashes of light controlled by the scanningdisc 30 in conjunction with thetube 29, leave their trace upon the tapes 89. It will be understood that a tape is provided for eachof the lam'ps 12. and in place of the photoelectric cell '35.

By this apparatus, permanent records of the messages transmitted are received, each tape bearing marks indicating the intermittent energization of the lamps 12. Thus the tapes s may be removed from the casing 88 and be translated at leisure. The relays used in connection with the photo-electric cells at the receiving end of the system, should be arranged electrically or mechanically so that their armatures will not be caused to flutter or vibrate between the beginning and the end of a component signal impulse: In this case it is understood that the instrument is ar- 5 ranged according to well-known electrical principles whereby the component impulses of a signal will be maintained-long enough next adjacent quadrant,

through the circuit= controller 81, an they are thus scanned 5 so on through the entire rotation arly to Fig. 10 of i to effect the same result as a single signal.

When only one signals areto be the normal'capacityof reception at a receiving station, ture shown in the scanning discs, may be-m the, form of-a long slot,'diametrically disposed, thereby allowing a maximum illumina tion from the neon 1i this connection also it will be seen that with a few-messages asthe normal desired capacity, larger cells may be used; seen also that the photo-electric cells in the receiver may be unconventionaliy placed, some being further away than others from the disc, instead of in a plane bank as illustrated. This allows larger cells to be used. It will be further obvious that any combination of, photo-cells may be used for messages at a at both the transmitter and receiver, 1n a well known way.

A number of banks of lights ma be used -at the transmitter and a correspon 'ng number of banks of photo-electric cells may be used at the receiver,.to effect aigreaterincrease in the number of messages possible. Transmission in this way may be carried out byproviding a circuit controller to allow only one bank at a timeto be in operation. I

Messages may be recorded in another way by displacing the relays associated with the photo-electric cells, with a magnetized tape device capable 'of recording magnetic im-- pulses according'to well known practice.

In connection with Fig.6, it will be seen that the relays themselves may operate the resistance rod direct; or the solenoids may be arranged to operate the piston against a controllable air pressure or pneumatic resistance instead of having a vacuum for this purpose. a i

It will be obvious that a plurality of segre gated simultaneous component signal 'impulses may be used to transmit one messagecharacter.

tus which will transmit a maximum number of messages simultaneously, a largenumber may still be transmitted simultaneously even iffour or five signals are taken for a single character. In connection with this feature, I have devised a mechanism which will en able an automatic printing or typewriting machine to be used effectively upon this principle. This mechanism is depicted in one form in Fig. 11 which is a diagram of the mechanism for the receiving end and shows how the lights are controlled at the transmitter.

Now referring toFig. 11, 91 is an automatic typewriting machine suitable for use in message transmission. This may be electhe small aperght to pass through. In p it will be further Although one of the main objects of my invention is the efl'ecting of an apparatrically operated, the closing of circuits effecting the printing of the keys. Accordingly, I have shown means for properly controlling these circuits. In this case I have shown five photo-electric cells, as this number is adequate for forming enough different combinations for all the keys of an ordinary typewriter. Obviously more can be used where more characters are to be transmitted, for instance in a machine where different types are used such as in newspaper work or typesetting where a system such as the present one, may be used. The photo-electric cells 92, are part of the signalreceiving system as set forth in this application, although the. present invention is not restricted to this specific arrangement in this connection. Each of these five cells is electrically connected to the primary coil of a relay 93, through a potential in a well known way. The local current of the relay serves to energize a solenoid 94 capable of closing another circuit, by making a contact with a member 95. The closing of this last circuit causes the key combination mechanism of the typewriting machine to be put into such a position that when another circuit 96 is closed the typewriter key will be caused to print, and t e key printed will be determined by thBSPGClfiO members of the combination effected. This circuit 96, or printing circuit, is closed when any of the relays 93 is energized by a signal, and inasmuch as the speed at which the five relays are affected will be'practically simultaneous, as set forth in my invention, the eifecting of the printing circuit 96 will not be accomplished until all the members of the combination control 95 have had ample, time to be put into control ling position. The breaking of the relay circuit at the end of a transmit-ted signal will not only cause the members 95 of the combination mechanism to be put into normal position, but will also cause the'printing circuit 96 to be put into normal position, by the breaking of circuit 96. Thls circuit 96 is broken when the relay armature 98 is in normal position, as the contacts 97 of circuit 96 are then apart. The closing of circuit 96 may be retarded as much as necessary according to'the speed of the message transmission segregating system, by arranging suitable electrical means such as resistance wire in the circuit, or by using some form of mechanical retardin means.

It wil be obvious in considering the in vention that other chan es ma be made in the invention without et-ractin-g from the merit thereof, or the spirit of the invention, particularly in r ard to the lights. For instance, instead 0 utilizing the perforated discs in the invention, with the accompanying mechanism for transmitting and receiving the segre ted message signals, it will be seen that revo I wlihg contacts may be used, thus in a somewhat different manner.

with receivin enabling the same results to be obtained but Sucha revolving contact device may be used only at one end if desired, while the perforated disc ggay be used at the other, as may be deemed st. When a revolving contact is used for lighting signal lights, the advantage is obtained of. enabling a stronger signal light to beo'btained, as there may be an individual light for each of the segregated signals, these being each as large and strong as the need requires, while withthe discs the light would necessarily be much weaker. Although the said revolving contacts may operate the relays direct, I prefer to have the lights regulate the current in photo-electric cells, as it will be found more eflicient principally because automatically when a signal is received as hereinbefore described. This feature is carried out by arranging a separate combination of signals for actuating the mechanism which operates the printing key according to and when the signal combination is received. This method of separately controlling the actual printing mec anism may be further varied by arrangin another or sixth segregated signal especially for this purpose.

From the foregoing it will be readily seen that a noveland improved method of transmitting a plurality of messages over a single circuit or upon a single carrier wave has been provided and that there has been provided in conjunction therewith a novel and improved synchronized means for use in connection and transmitting scanning discs of television apparatus or the like. The invention also provides means for the transmission of piano or similar key impulses and also rovides for the separate recording of a p urality of simultaneously transmitted messages.

It will also be understood in connection with the present invention, that numerous changes and modificationsof the structural details and the full use of equivalents may be resorted to without departing from the cludes the energizing of a plurality-of lights Ill spirit or scope of the present invention as v by a plurality of associated signal devices,

and successively and intermittently superposing light from saidlights upon light re-- sponsive means topropagate a single signal in response to said intermittent and successive superposin of said lights.

2. A commumcation apparatus, including a plurality of light sources individually paratus adapted to broadcasta signal moduenergized by associated .signal devices, a ,lated in accordance with the energization of photoelectric cell, and means interposed besaidv cell, and a receiving apparatus includ tween said cell and. said light sources for ing a light source controlled by said broad- 6 i di ll d successively permitting cast signal and a scannin disc for segregatv I projection of light. from said sources to said ing th componen ig 8 .f Said broadphoto'electric cell. castsrgnal.

3. A communication apparatus, including ALBERT B. CLARK.

a bank of individually energized light 10 sources, scanning means for said bank, and g a 75 a photoelectric cell successively energized by the individual lights of said bank and ,the transmission of a single signal by said photoelectric cell.

4. 'A. communication apparatus, including 1 g a signal device for separately'actuating sepa- Y rate light sources in a bank of light sources, 4 television means for combining and subsequently dividing the signals, and photoelectric means for retransmitting separate 7 4 v 86 signal impulses inresponse to said signal device. 7 t

5. A method of communication, which in- "cludes the step of simultaneously propagating a plurallty of signals, energizmg a Q photoelectric cell by successive portions of said signals, and propagating a signal wave in response to the energization of said cell.

6. A method of communication, which in-' eludes the step of simultaneously propagatv I A ing a plurality of signals, energizing a light source in response to each signal propagated, operating a scanning disc before said lights, energizing a photoelectric cell by light transmitting through said scanning disc, and i propagating a single signal in res nse to the energization of, said photoelectrlc cell.

7. A communication apparatus including aplu'rality of light sources individually energized by associated signal devices, a photo- I electric cell, and a scanning disc interposedbetween said cell and said light sources for periodically and successively permittingprojection of light from said sources to said photoelectric cell. I

8. A communication apparatus, including a plurality of light sources individually energized by associated signal devices, a photoelectric cell, a scanning disc interposed between said cell and said'light sources for periodically and successively permitting projection of light from said sources to said photoelectric cell, and a signal broadcasting a apparatus adapted to broadcast a signal modulated'in accordance with the energization of said cell.

9. A communication apparatus, including ,a plurality of 'light' sources individually v Menergized i-by associated signal devices, a f

I 5 photoelectric ce photoelectric cell, a scanning disc interposed between said cell and said light sources for periodically and successively permittingv 'i projection of light from said sources to said l, a signal broadcasting ap- 

